ANNOTATIONS AND ADDITIONS. 101 



relations given by me in the Dictionnaire des Sciences 

 naturelles, T. xviii. 1820, p. 422-436; and in the Annales 

 de Chimie et de Physique, T. xvi. 1821, p. 267-292.) 



The numerical relations of the forms of plants, and the 

 laws observed in their geographical distribution, may be con- 

 sidered in two very different ways. If plants are studied in 

 their arrangement according to natural families, without 

 regard to their geographical distribution, it is asked, What 

 are the fundamental forms or types of organisation to which 

 the greatest number of species correspond ? Are there on 

 the entire surface of the earth more Gluinaceae than Compo- 

 sitse ? Do these two orders make up between them one- 

 fourth part of the whole number of phsenogainous plants ? 

 What is the proportion of Monocotyledons to Dicotyledons ? 

 These are questions of General Phytology, or of the science 

 which investigates the organisation of plants and their 

 mutual connection, or the present state of the entire vegetable 

 world. 



If, on the other hand, the species of plants which have 

 been grouped according to the analogy of their structure are 

 considered, not abstractedly, but according to their climatic 

 relations, or according to their distribution over the surface 

 of the earth, we have questions offering quite another and 

 distinct interest. We then examine what are the families 

 which prevail more in proportion to other Phanerogamse in 

 the torrid zone than towards the polar circle ? Are Com- 

 positse more numerous, either in the same geographical lati- 

 tudes or on the same isothermal lines, in the New than in 

 the Old Continent? Do the forms which gradually lose 



